The beginning of Season Three finds the Robinsons having to make emergency evacuation procedures because of an approaching comet, from the planet they have been marooned on for the previous twenty-seven episodes.
Once in flight again, the Robot is swept out into space because of Dr. Smith's carelessness and the Robot is apparently lost.
The Robinsons soon come across and make a landing on top of some sort of ship, where the Robot is then reunited with the family.
The ship is a prison ship, named the Vera Castle, and it is filled with hundreds of frozen prisoners.
(According to the Robot, the actual count of prisoners aboard the ship is 9,874.)
The prisoners have all been held captive way past their normal sentences due to a chronometer on the ship which has been frozen for over two-hundred years.
Professor John Robinson repairs the time clock in a few moments, and the prisoners are immediately freed. MGM's Robby the Robot makes his second appearance, this time as a prison guard, and he threatens Professor Robinson and Major West's attempt to obtain a much needed propulsion system for their spaceship, the Jupiter Two.
In this episode brand new uniforms are unveiled, along with an all-new title theme for this final season of the series.